A conventional electro-acoustic transducer (hereinafter referred to as transducer) is described referring to FIG. 8 through FIG. 13. FIG. 8 through FIG. 10 show cross sectional views of conventional transducer working as the speaker, or as the receiver, in a portable telephone unit or the like electronic apparatus. As shown in FIG. 8, magnet 1 is disposed between upper plate 2 and yoke 3 constituting an inner-magnet type magnetic circuit 4. Yoke 3 of magnetic circuit 4 is press-fit in resin frame 6, and integrated by gluing. Diaphragm 7 is fixed to frame 6 at the circumference. Voice coil 8, which is for vibrating diaphragm 7, is attached to diaphragm 7, at the same time it is placed in magnetic gap 5 of magnetic circuit 4.
Lead wire of voice coil 8 is soldered with one end of terminal 10. Frame 6 is provided with terminal 10, which is molded partially in the frame. Terminal 10 is bent-up at its approximate middle into two portions so that it is not stretching out beyond the outer boundary of frame 6. The other end of terminal 10 is designed to work as the electrical terminal to be coupled with a system of an apparatus. Terminal 10 is formed by bending a conductive sheet metal, and makes contact with an electric supply section of a system taking advantage of the spring force of sheet metal. One end of terminal 10's sheet metal is folded inward to constitute stopper 9; which stopper is expected to restrict terminal 10 not to be bent beyond the reversibility limit value of the metallic material.
FIG. 9 and FIG. 10 are cross sectional views, showing terminal 10 of FIG. 8 at its different states. Assuming that FIG. 8 shows terminal 10 at its top dead point, FIG. 9 illustrates terminal 10 at its bottom dead point. FIG. 10 shows a state of terminal 10 where it is undergoing too much force which was given further after terminal 10 reached the bottom dead point, and stopper 9 was deformed and collapsed.
FIG. 11 and FIG. 12 are cross sectional views, showing the above-described transducer being assembled in a portable telephone unit or the like electronic apparatus. FIG. 11 shows a state where terminal 10 is moderately bent, and the telephone unit's electric supply section is kept pressed with an appropriate spring force. FIG. 12 shows a state when a portable telephone unit is dropped, for example. Due to the impulsive force, which was caused as the result of an external factor, terminal 10 was pushed by the telephone unit's electric supply section and bent to reach the bottom dead point, furthermore, an excessive force was additionally given to, and stopper 9 was deformed and collapsed. In the illustrated case, the bent sections of stopper 9 and terminal 10 were deformed beyond the reversibility limit value of the metallic material. So, once it is hit by such a shock force, it is difficult for them to return to their original states even after the force is withdrawn.
A transducer of the above-described structure has been disclosed in Japanese Patent Unexamined Publication No. 2003-37890.
Portable telephone units or the like electronic apparatus containing the above transducer sometimes have to undergo rough handling of users; these apparatus can be treated roughly, even dropped to the ground and damaged. Therefore, there has been a strong voice from the market for an enhanced reliability with these kinds of electronic apparatus. In order to raise the reliability with apparatus, it is indispensable to enhance the reliability of a transducer incorporated in apparatus.
In the conventional transducers, or the speakers, receivers, their connection with electrical supply section of a system relies upon the spring force of sheet metal constituting terminal 10. However, in a case where much dimensional margins are provided for assembling a speaker into an apparatus body, stopper 9 of terminal 10 might get deformed when a speaker is pushed in an apparatus body during assembly; then, terminal 10 can be bent beyond the reversibility limit value of the spring force of the metallic material. Or, when a portable telephone unit or other such electronic apparatus is dropped by careless handling, stopper 9 of terminal 10 may be collapsed by a substantial impulsive force, and terminal 10 may sometimes be bent beyond the reversibility limit value of the spring force of the metallic material. Although stopper 9, which is formed of the same metallic material, is provided with a spring force, it can also be deformed permanently when a strong force is applied exceeding the reversibility limit value. This is the mechanism how the above-described problem arises. Then, the respective spring forces of terminal 10 and stopper 9 deteriorate; as the result, the contact with electrical supply section of an apparatus becomes instable. Problem will appear under such a situation; signal transfer can be readily interrupted due to contact error whenever an apparatus is hit by an impulsive force or it is exposed to vibrating motion. This is not a problem peculiar to the above-described configuration where stopper 9 is formed at the end portion of terminal 10, but the same problem may arise in the other configuration illustrated in FIG. 13, where stopper 11 is formed integrally with the same resin when a frame is molded through injection. In the latter configuration, once resin stopper 11 is damaged by an impulsive force, terminal 10 is bent beyond the reversibility limit value of the spring force of the metallic material.